Slurry storage and liquid injection arrangement for preventing plug formation in a shut-down slurry pipeline

ABSTRACT

Method and apparatus for preventing plug formation in a shutdown slurry pipeline. Upon pipeline shutdown, slurry is removed from those portions of the pipeline in which plug formation caused by slumping and compacting of the slurry solid phase under the force of gravity is likely to occur. Substantially simultaneously with this operation, slurry liquid phase material, i.e., the slurry carrier, is introduced into the pipeline.

United States Patent Inventor Moye Wicks, III

Houston, Tex. 860,342

Sept. 23, 1969 July 1 3, 1971 Shell Oil Company New York, N.Y.

Appl. No. Filed Patented Assignee SLURRY STORAGE AND LIQUID INJECTION ARRANGEMENT FOR PREVENTING PLUG FORMATION IN A SHUT-DOWN SLURRY PIPELINE 3 Claims, 5 Drawing Figs.

US. Cl 302/14, 302/66 Int. Cl B65g 53/30 Field of Search 302/14,15, 16, 66, 36, 17, 28

[56] References Cited UNlTED STATES PATENTS 2,631,899 3/1953 Jullien 302/14 2,903,301 9/1959 Pfening 302/28 Primary Examiner-Andres l-l. Nielsen Attorneys-Thomas R. Lampe and J. H. McCarthy ABSTRACT: Method and apparatus for preventing plug formation in a shut-down slurry pipeline. Upon pipeline shutdown, slurry is removed from those portions of the pipeline in which plug formation caused by slumping and compacting of the slurry solid phase under the force of gravity is likely to ac cur, Substantially simultaneously with this operation, slurry liquid phase material, i.e., the slurry carrier, is introduced into the pipeline.

PATENTEU JUL 1 3|91| FIG. 4

INVENTOR:

MOYE WICKS,III BY;

HIS ATTORNEY FIG.

SLURRY STORAGE AND LIQUID INJECTION ARRANGEMENT FOR PREVENTING PLUG FORMATION IN A SHUT-DOWN SLURRY PIIELINE The present invention relates to pipeline transport operations; and, more particularly, to a method and apparatus for preventing the formation of plugs caused by the downward movement and compacting of slurry solids in an inclined portion of pipeline during a shutdown period.

Transportation by pipeline is a major and growing industry. With the use thereof formerly confined almost entirely to movement of water, gas and petroleum products, pipelines, with the advent of slurry transport, have become useful for long and short hauls of wide variety of raw materials and finished products.

With respect to the pipeline transportation of materials in slurry form, problems arise when such materials are moved through pipelines inclined to go over a hill or down into a valley. At these locations, during a planned or emergency line shutdown, the solids of the transported slurry may settle out vertically and subsequently slide down the inclined portions of the pipeline, thereby causing a compacted plug which may be very difficult to dislodge and move when line shutdown is terminated and transport activities are resumed.

These difficulties can sometimes be avoided by laying solids carrying or slurry pipelines so that they do not exceed a slope or angle of inclination above which sliding occurs. Alternatively, the pipeline can be emptied at each shutdown. Obviously, these alternative prior art approaches are not always feasible or economical, especially in those situations where long and relatively steep slopes are encountered. Slopes of this nature are being encountered with increasing frequency as pipeline operations are being extended to new relatively inaccessible mountainous areas in the United States and elsewhere.

SUMMARY OF THE INVENTION It is therefore a primary object of the present invention to provide an improved and economical apparatus and method whereby slurry material being transported in an inclined pipeline section is prevented from producing a plug in a pipeline during a shutdown.

This and other objects have been attained in the present invention by providing a method and apparatus for preventing plug formation in a shut down slurry pipeline wherein storage tanks are located at predetermined intervals along the pipeline in those locations where plug formation is likely to occur. When the pipeline flow rate falls below some predetermined minimum value, slurry from the pipeline is transferred. to the tanks, as by means of gravity or pumps, for example. Substantially simultaneously with the transfer of slurry material to the tanks, slurry liquid phase material, i.e., the carrier fluid, is injected into the pipeline. The slurry is stored in the same tank used to accommodate the injected liquid.

DESCRIPTION OF THE DRAWING The above-noted and other objects of the present invention will be understood from the following description, taken with reference to the accompanying drawing. In describing the invention in detail, reference will be made to the drawing in which like reference numerals designate corresponding parts throughout several views in which:

FIG. I is a diagrammatic view illustrating a given length of slurry pipeline which has been modified in accordance with the teachings of the present invention;

FIG. 2 is an enlarged cross-sectional view in longitudinal projection illustrating an inclined portion of the pipeline section of FIG. I with a slurry storage and liquid injection arrangement in operative association therewith in accordance with the teachings of the present invention;

FIGS. 3 and 4 are cross-sectional views in reduced scale illustrating the storage tank of FIG. 2 in different operative conditions; and

FIG. 5 is a view similar to that of FIGS. 3 and 4 but illustrating an alternative form ofstorage tank.

Referring now to FIG. 1, a given length of slurry pipeline 11 is illustrated in the position assumed thereby as the pipeline proceeds to and from a valley formed between two hills or mountains I2 and 13. The terrain illustrated is typical of that encountered in pipeline laying activities, although it should be understood that the teachings of the present invention may be carried out in any topographical configuration wherein a portion of slurry pipeline is inclined.

The transportation of slurries consisting of solid particles in a fluid medium by use of pipelines similar to that disclosed in FIG. I is quite well known, and such expedient is finding increasing use, especially in those situations where the source of raw materials is relatively remote and inaccessible from the point ofdelivery, which may be a suitable processing plant, for example. in the disclosed arrangement, it may be assumed for purposes of illustration that the slurry material being transferred through pipeline 1 I as by means of conventional pumps (not shown) is moving through the line in the direction indicated by the arrows. However, the teachings of the present invention are, of course, applicable regardless of the direction of flow of the slurry.

As long as flow continues at or above some critical rate in the pipeline, the solid matter of the slurry will remain in suspension within the pumped liquid, even when thesolid matter has a higher specific gravity than the liquid, If, however, the flow is stopped for any reason, ie, the pipeline is shut down, such solid matter will settle out of suspension. In the situation where the line is horizontal or the slope of the line is insufficient to cause sliding of the settled solids, no problem is created by such settling out. Under these conditions, a liquid-rich channel remains open at the top of the line which allows the settled material to be resuspended with a minimum of difficulty upon resumption of slurry flow.

A serious problem can exist when the pipeline must be inclined to go over a hill or down a valley, as illustrated, for example, in FIG. I. At these locations, the settling of solids followed by their sliding down the slope during a protracted shutdown can result in a compacted plug of material difficult, if not impossible, to move or resuspend by normal operating procedures. In the illustrated pipeline configuration, such solids would slide downwardly into the valley formed between hills or mountains l2 and 13. The solid material would then compress under its own weight to form a plug in the valley in an obvious manner.

Such plug formation is prevented in accordance with the teachings of the present invention as follows. Disposed adjacent to the inclined portions of pipeline II, i.e., those portions where slumping of slurry solid phase material is likely to occur under the influence of gravity, are :"un storage and fluid injection devices 21 and 22, constructed in accordance with the teachings of the present invention.

The devices 21 and 22 are of identical construction and in the interest of simplicity reference should be had to FIG. 2 wherein device 21 is illustrated in detail. Device 21 comprises a tank 31 defining an interior which is divided in a fluidtight manner across the central portion thereof by a partition or wall 32 to define two compartments 33 and 34 which are of substantially equal size when the partition is in the unstressed condition shown in FIG. 2. Partition or wall 32 is preferably constructed of a flexible membrane material of any suitable type which is chemically inert with respect to the slurry material being transported within pipeline 11. An example of a membrane material suitable for many applications is neoprene rubber.

In communication with chambers 33 and 34, respectively, are conduits 35 and 36 which lead to pipeline 1] and are in communication with the throughbore defined by said pipeline. Pumps 41 and 42, which may be of any suitable conventional type, are operatively associated with conduits 35 and36 as shown.

In operation, one of the two compartments of the tank 31 would be kept full of liquid material identical to the liquid phase or carrier fluid of the slurry pipeline 11. While either compartment may be used for this purpose, it will be assumed for the sake of illustration that compartment 33 is the one in which the liquid is maintained. The force of the liquid material causes the flexible partition or wall to extend in flexible partition or wall 32 to extend in the manner shown in FIG. 3, thereby permitting substantially the entire tank 31 to be filled with the liquid material within the expanded compartment 33.

As slurry flow within pipeline ll terminates. pumps 41 and 42 are actuated. Pump 41 forces the liquid material out of compartment 33 and into the interior of the pipeline 11 while pump 42 substantially simultaneously removes slurry from the pipeline and forces it into compartment 34 of tank 31. This operation continues until the wall or partition 32 reverses itself within the tank and assumes the position shown in MG. 4.v

At this point, sufficient slurry will have been removed from pipeline 11 to prevent compacting and plug formation by the solid phase thereof under the influence of gravity. Upon pipeline restart, the slurry in compartment 34 is reinjected into the pipeline and compartment 33 is refilled with slurry liquid phase material from a suitable source ofsupply.

It may be seen that the present arrangement has the advantage that a single storage unit may be used to accommodate both the liquid material to be injected in the pipeline and the slurry material. Rather than use a flexible membrane for dividing the storage tank into separate compartments a pistonlike divider such as that shown in FIG. and designated by reference numeral 51 may be used for this purpose. it will be readily understood that divider 51 conforms in shape to the inner wall of tank 31 so that it is freely slidable with respect thereto while at the same time forming a liquidtight seal. Upon introduction of material into the tank on one side of the divider 51 it will move in the opposite direction in an obvious manner to maximize storage space in the tank.

I claim as my invention:

1. Apparatus for preventing plug formation in a shutdown pipeline used to transport slurry material including a solid phase and a liquid phase, said apparatus comprising:

a storage tank located adjacent to said pipeline in a location where slurry solid phase material is likely to slump and compact under the influence of gravity upon pipeline shutdown;

divider means operatively disposed in said tank to divide the interior of the tank into two compartments in a fluidtight manner, said divider means being relatively movable with respect to said tank so that the sizes ofsaid compartments may be varied; and

pump means operatively associated with said tank and said pipeline whereby material may be transported from one of said compartments to the pipeline and from the pipeline to the other of said compartments with the movement of said divider means relative to said tank being responsive to transport of said material by said pump means.

2. Tl-le apparatus of claim 1 wherein said divider means comprises a flexible wall affixed to the inner wall of said tank about the periphery thereof in a fluidtight manner.

3. The apparatus of claim 1 wherein said divider means comprises a piston movable mounted in said tank and having an outer peripheral surface conforming to the shape of the inner wall of the tank. 

1. Apparatus for preventing plug formation in a shutdown pipeline used to transport slurry material including a solid phase and a liquid phase, said apparatus comprising: a storage tank located adjacent to said pipeline in a location where slurry solid phase material is likely to slump and compact under the influence of gravity upon pipeline shutdown; divider means operatively disposed in said tank to divide the interior of the tank into two compartments in a fluidtight manner, said divider means being relatively movable with respect to said tank so that the sizes of said compartments may be varied; and pump means operatively associated with said tank and said pipeline whereby material may be transported from one of said compartments to the pipeline and from the pipeline to the other of said compartments with the movement of said divider means relative to said tank being responsive to Transport of said material by said pump means.
 2. THe apparatus of claim 1 wherein said divider means comprises a flexible wall affixed to the inner wall of said tank about the periphery thereof in a fluidtight manner.
 3. The apparatus of claim 1 wherein said divider means comprises a piston movable mounted in said tank and having an outer peripheral surface conforming to the shape of the inner wall of the tank. 